WASHINGTON, DC - FEBRUARY 15: The American flag above the White House is lowered to half staff following the shooting yesterday at Marjory Stoneman Douglas High School on February 15, 2018 in Washington, DC. U.S. President Donald Trump is expected to address the nation later today in response to the shooting in Parkland, Florida where 17 people died. (Photo by Win McNamee/Getty Images)

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The FBI was warned in September about a possible school shooting threat from a YouTube user with the same name as the suspect in Wednesday's campus massacre in Parkland, Florida, according to a video blogger.

Ben Bennight, the 36-year-old YouTube video blogger from Mississippi, noticed in September an alarming comment on a video he'd posted. He told CNN he immediately contacted the FBI.

"Im going to be a professional school shooter," read the comment, left by a user with the name Nikolas Cruz, the same name of the suspected shooter who opened fire at Marjory Stoneman Douglas High School on Wednesday, killing at least 17 people.

Bennight emailed a screenshot of the comment, which he shared with CNN, to what he thought was an FBI tip line, but the email address was invalid, he said. Bennight said he followed up with a phone call to the FBI. The comment on YouTube has since been pulled down.

According to Bennight, agents from the FBI's field office in Mississippi contacted him and came to his office to conduct an in-person interview the next morning. Bennight told the agents he didn't know anything about the user, he told CNN.

That was the last contact he had with the FBI until Wednesday, he said.

It's not clear whether the FBI ever made contact with the individual who left the YouTube comment. The FBI and the bureau's Mississippi field office did not immediately respond to CNN's requests for comment.

Then, on Wednesday afternoon, after Cruz was arrested, Bennight got a call from an agent in the FBI's Miami field office, who wanted to follow up on the September incident, he said. A few hours later, FBI agents from the Mississippi office paid Bennight another visit.

"I saw the story kind of go across my newsfeed but I didn't pay a whole lot of attention to it, but when the FBI said it was the same name the first thing that went through my mind was, 'Wow, I hope you were at least watching this guy that I alerted you to months ago,'" he recalled Thursday in a phone interview with CNN.